Tobacco companies are rejecting suggestions by Otago University researchers that they aren't following the rules on displaying graphic warning images on cigarette packets.
Researcher Janet Hoek says a study has shown that the most disturbing warning images of the effects of smoking appear on fewer packets than the least offensive pictures.
Tobacco companies are required to print the seven pictures on packets in equal numbers.
But Imperial Tobacco says it doesn't accept the analysis, which was based on 1208 packets. The company says it has told its printers to print each image the same number of times.
British American Tobacco also rejects the suggestions, saying that its graphic warnings meet the legal requirements.
Professor Hoek says the results suggest that tobacco companies are trying to reduce the impact of government health warnings by limiting the frequency of the most disturbing images.